66 Thomas Albert Williams 



culate; VI very short. Legs brownish, with yellowish bases. Tarsi black- 

 ish. Wings with rather heavy blackish veins, the three oblique veins 

 originating equidistant ; first and second discoidals only slightly if at all 

 curved ; cubitus often with but one branch. Stigma lanceolate, acute at 

 both ends, dirty white. Stigmal vein prominent, sharply curved. Honey 

 tubes rimmed at the tip, dusky, greenish at base, not reaching to tip of 

 abdomen, about twice the tarsi. Tail short, knobbed, hairy. Length of 

 body about 1.90 mm., to tip of wings about 3.25 mm. 



All forms are more or less covered with capitate hairs, the 

 winged form having them on the head and antennae principally. 

 Oestlund describes a species on Potentilla anserina under this 

 name but afterwards concludes that it is Myzus rosarum. My 

 specimens are very different from that species and produce quite 

 a different effect on the plant. 



On Potentilla argnta. Ashland, May 24, 1890. On the under 

 side of the leaves, causing them to curl up. 



Cotypes in the collection of the University of Nebraska (nos. 

 T07, 108) and of the U. S. National Museum (no. 376). 



S3. Myzus ribis (Linnaeus). 



Linnaeus, Syst. Nat., II, p. 733 (1767). Aphis ribis. 



Kaltenbach, Mon. Pflan., p. 39 (1843). Aphis ribis. 



Fitch, Trans. N. Y. Ag. Soc, XIII, p. 435 (1856). Aphis ribis. 



Koch, Die Pflan., p. 39, figs. 50, 51 (1854). Rhopalosiphum ribis. 



Passerini, Gli afidi, p. 31 (i860). Myzus ribis. 



Buckton, Mon. Brit. Aph., I, p. 180, pi. XXXIV, figs. 1-4 (1876). 

 Myzus ribis. 



Thomas, Ins. 111., 8th Rep., p. 76 (1879). Myzus ribis. 



Oestlund, Syn. Aph. Minn., p. 74 (1887). Myzus ribis. 



Weed, Psyche, V, p. 210 (1889). Myzus ribis. 

 Apterous viviparous female: Elongate oval. Color yellowish green, more 

 or less mottled with dark green. Antennae thread-like, as long as or 

 longer than the body, on gibbous frontal tubercles and I gibbous, pale ; 

 whole body more or less covered with whitish, capitate hairs or bristles. 

 Front very bristly. Legs pale, with dusky tarsi. Honey tubes slender, 

 0.50 mm. long, often slightly clavate, pale. Tail short and conical, hairy, 

 pale. 



Winged viviparous female: Head and thorax olive brown to black. An- 

 tennae longer than the body, black; III and IV with sensoria; VII much 

 the longest. Beak rather long. Wings large, with yellowish insertions; 

 veins dusky yellowish; stigma dirty white. Legs pale, with dusky joints 

 and tarsi. Abdomen with more or less distinct marginal spots and trans- 



150 



